Induction heating of metals to cause the metal to raise the temperature of associated materials is well known and has been employed to cause the curing of adhesives and/or plastics associated with the metal. However, since plastics and metals are substantially dissimilar from each other in their chemical makeup, a proper bond between the plastic and metal is often times not easily achieved. While there are many applications where the strongest possible bond between plastics and metals would materially enhance the commercial utilization of such combinations of materials, one area which has particlarly strong needs for a good plastic-to-metal bond is the munitions industry.
In small caliber arms capable of rapid fire of many rounds in a short period of time, it is quite naturally desirable that the velocity of the projectile be maximized while the accuracy, primarily related to the spin thereof, of the projectile is additionally of prime importance. Normal manufacture of these types of arms includes the addition of rifling in the barrel of the arms and metallic bands on the projectile for the purpose of imparting spin to the fired projectile as it passes through the barrel.
Since these types of arms are intended to be fired rapidly and for long periods of time, it has not been possible to design a rifled barrel which can withstand the wear of many rounds of metal bands through the barrel in contact with the rifling. Further, as the velocity of the projectiles is increased, most common metallic bands will plate onto the inside of the barrel thereby decreasing performance. For that reason, plastic rotating bands have been provided on the rounds to engage the rifling without damage thereto and impart the spin to the projectile.
The projectile is subjected to significant acceleration upon firing, both in the axis of the direction of flight and in rotation due to the rifling. A strong bond between the rotating band and the projectile is of absolute importance if a satisfactory projectile is to be made.